I'm using iMovie to make youtube vids for a friend. He's a musician, so it's just the song with album art or some kind of still image. I'd like to know how to make this image change color, fading through all the colors in the spectrum continuously..

I'm using iMovie to make youtube vids for a friend. He's a musician, so it's just the song with album art or some kind of still image. I'd like to know how to make this image change color, fading through all the colors in the spectrum continuously..